I find the best way to trouble shoot these is cap the sprinkler heads and turn on the water. If one out of 3 is working, dig it up, unscrew it from the riser and thread on the appropriate sized cap. Turn on the water. See if the other two come up, or water starts finding its way to the surface. You can usually tell if water is still running through the lines by the sound, or you may need to use the tell tale on the meter.

If no water is moving, you likely have a blockage or pinch. If you have water moving through the lines with the one working head capped, the leak is normally after that head and before the next one that won't come on.

If one sprinkler is working and two are not, why are you even doing anything with the valve? Obviously it is working and the problem is either in the pipe to those two heads, or the heads themselves. Your diagnostic abilities are flawed and you probably need an expert to repair the problem.